Process for splitting off nitric acid from organic nitrate compounds



United States Patent Ofitice 3,157,690 Patented Nov. 17, 1964 3,157,690 FRUCESS FOR SPLITTING OFF NITRIC ACID FROM ORGANIC NITRATE COMPOUNDS Walter Fink, Zurich, Switzerland, assignor to Monsanto Company, a corporation of Delaware N Drawing. Filed June 16, 1961, Ser. No. 117,515 Claims priority, application Switzerland July 18, 1960 7 Claims. (Cl. 260-4653) wherein A is a known activating group, especially an olefin, cyano or carbonyl group. Such compounds are 3- nitrato-olefins, -nitriles, -aldehydes, -ketones, -carboxylic acids and their derivatives such as esters, amides, halogenides, and anhydrides, also thiocarboxylic acids and their derivatives. The valencies not yet occupied in the formula can be filled optionally, as far as these substituents do not hinder the exchange of the nitrate radical for the fluorine atoms. Instead of nitrate groups other groups such as nitrate and sulfate groups can be split oif by the process of the invention.

The splitting off of nitric acid occurs with the formation of a double bond between the or. and ,B-carbon atom according to the following scheme This process is described in copending application Se-' rial No. 62,881, filed October 17, 1960. These com pounds are valuable for carrying out the present process of invention. They contain on the rat-carbon atom, apart from a hydrogen atom which is indispensable for the reaction, always a chlorine atom. This chlorine atom is maintained on the denitratization and unsaturated halogen containing end products are formed corresponding to the type when the activating group is an olefin group as likewise on splitting off nitric acid from The latter compound is obtainable by the addition of chloronitrate to 1,3-butadiene.

For carrying out the reaction, the defined starting roducts which contain in the ii-position a nitrate group are brought into an intimate contact with an at least double molar amount of a hydrogen fluoride salt, being preferably finely divided potassium fluoride. The amount of potassium fluoride is hereby based on the present nitrate groups. When, for example two nitrate groups are to be split off, an at least fourfold molar amount of potassium fluoride is necessary according to the theory. In general, an excess of potassium fluoride or of other fluoride will be used. It is supposed that the reaction occurs in two steps. With, for example, l-chloro-Z-nitratopropionitrile as follows:

In the first reaction step, the exchange of the nitrate group for fluorine occurs. In the second reaction step, hydrogen fluoride is surprisingly easily split off, due to the catalytic activity of potassium fluoride. The hydrogen fluoride being set free is bound by the potassium fluoride and can be removed from the reaction mixture together with it. The denitratization by the new method can be carried out with or without the use of a solvent.

But, the splitting off of nitric acid from l-chloro-Z-ni- 'trato-compounds is generally done in a solvent, in order to avoid any decomposition of the unstable nitrate compounds which are generally prepared by using a solvent.

Suitable solvents are C01 CC1 F, CCl I-l etc. The reaction temperature conforms to the instability of the nitrate containing starting products. Conveniently it is between about 2040 C. The reaction time normally is about 4-6 hours, but in particularcases it may be essentially shorter. Corrosion-proof vessels manufactured from VZA, V4A, Hastelloy, graphite, quartz, ceramic etc. are used in the process.

For the isolation of the unsaturated reaction roducts the excess potassium fluoride together with the KP-HF and KNO which are formed in the reaction, is filtered ofi. This method is recommended with compounds which are unstable and easily oxidized such as unsaturated aldehydes. The reaction product can also be fractionally distilled, if need for, under reduced pressure without a previous filtration.

If desired, anti-oxidants may be added to the reaction mixture. The use of a particular polymerization inhibitor is not necessary in the process of invention, because the salts which are. present in the reaction mixture are very efficient in this respect. Among the different fluorides such as KP, NaF, K TiF All Zn'F etc. which have been examined until now, only zinc fluoride, besides potassium fluoride, has been found to be slightly active for the den-itratization of p-nitrato-olefin compounds, p-nitr-ato-carbonyl compounds, e-nitrato-cyano compounds etc.

Now, it has yet been demonstrated for the first time that nitric acid can be split ofl? from certain B-nitrato compounds by potassium fluoride at low temperatures, it is clear that possibly other appropriate fluorine salts may be found. But it seems that KF is the cheapest and most convenient substance for this purpose.

EXAMPLE 1 25.6 g. of NO CH -CHClCOOC H (0.13 mole) in 50 ml. of CC1 =F are strongly stirred with 20 g. of KF (0.34 mole) at 25 C. for 5 hours. Then, the reaction mixture is fractionally distilled.

Yield: 8.5 g. (=48%) CH CClCOOC H B.P. 4l-43 C./15l6 mm.

EXAMPLES 2-4 It is proceeded as indicated in Example 1. The results are shown in the following Table 1.

Table 1 Denitratization of a-chloro-fl-nitrato compounds Boiling Yield, B-Nitrato Compound Product Point, per- (IL/mm. Hg cent;

NOaCHnCIIClCOOCaHs. CH1=CClCOOCzH5 4143/1546 3948 'NOaCHzOHClCOCHs CH2=CClCOCHa 28-32/11 15 NOaGHgCHOlGOOH--- OHz=CClQOOH 178179/722- 53 NOQOHZ'CHClOHO OH=CClCHO v chloro-fi-nitnato-thiolpropionic acid and the like, substituted in place of ethyl a-chloro-fi-nitratopropionate in an equimolar quantity in the experiment of Example I would produce the corresponding olefin. Of the esters and ketones especially desirable reactants are those in which the A group is a -COOR or COR group wherein. R is an aliphatic, preferably alkyl, hydrocarbon radical having not more than 6 carbon atoms.

Although the invention has been describedwin terms of specified embodiments which are set forth in considerable detail, it should be understood that thi's is by way of illustration only and that the invention is not necessarily limited thereto, since valternative embodiments and operating techniques will become apparent to those skilled in the art in view of the disclosure. Accordingly, modificationsare contemplated which can be made without departing from the spirit of the described invention.

What I claim is:

1. A process for splitting off nitric acid from compounds of the formula wherein A is selected from the class consisting of COOH,

CN, CH0, and COR "and GGORradicals wherein Ris aliphatic hydrocarbon having from 1 to 6 carbon atoms, and is the "chlorine atom, comprising treating the nitrate compounds at a temperature in the range of about 20- --40 C., with at least double the stoichiometric amount of potassium fluoride based on the amount of nitric acid to be split 01?. p

2. A process of claim 1 wherein the reaction is carried out in the presence of an inert solvent.

3. A process of claim 2 wherein A is a -COOR group and R is aliphatic hydrocarbon having from 1 to 6 carbon atoms. i

4. A process of claim 2 wherein A is a COR group and R is aliphatic hydrocarbon having from 1 to 6 carbon atoms.

5. A process of claim 2 wherein A is the aldehyde 6. A process of claim 2 wherein A is the cyano group. 7. A process of claim 2' wherein A is thecarboxyl group. I

No references cited. 

1. A PROCESS FOR SPLITTING OFF NITRIC ACID FROM COMPOUNDS OF THE FORMULA 